The present invention relates to a fluid dynamic bearing evaluating method for measuring a clearance of a fluid dynamic bearing by an electrical method.
A conventional fluid dynamic bearing evaluating method flows a current between a fixed member and a rotating member in a rotating state in a state, a space between the fixed member and the rotating member having been filled with an oil (lubricating fluid). The electrifying state of the fluid dynamic bearing is measured by a change in voltage.
According to the aforementioned conventional fluid dynamic bearing evaluating method, it can be determined whether the rotating member and the fixed member are in a contact state or in a noncontact state. However, a clearance between the rotating member and the fixed member cannot be quantitatively determined, and therefore, the characteristics of the fluid dynamic bearing cannot be clearly determined.
Accordingly, an object of the present invention is to provide a fluid dynamic bearing evaluating method capable of quantitatively determining the clearance between the rotating member and the fixed member in an operating state and determining the characteristics of the fluid dynamic bearing more in detail in the operating state.
In order to achieve the aforementioned object, the present invention provides a fluid dynamic bearing evaluating method for evaluating a fluid dynamic bearing, comprising the steps of:
filling a space between a fixed member and a rotating member with an uncharged lubricant,
flowing a current between the fixed member and the rotating member and measuring an electrical resistance value of the fluid dynamic bearing including the lubricant.
According to the present invention, the lubricant placed between the fixed member and the rotating member is not electrically charged. Therefore, the electrical resistance value measured in the operating state has a correlation with the clearance between the fixed member and the rotating member, and the clearance can be quantitatively determined by this electrical resistance value.
Moreover, perpendicularity of an axial bearing surface of the fixed member and an axial bearing surface of the rotating member in the operating state also has a correlation with the electrical resistance value. Therefore, the perpendicularity of the axial bearing surfaces can be quantitatively evaluated by this electrical resistance value. Moreover, the resistance value of the lubricant increases when the lubricant is deteriorated by oxidation, and therefore, the degree of deterioration of the lubricant can be quantitatively evaluated by the electrical resistance value.
Therefore, according to the fluid dynamic bearing evaluating method of the present invention, the operating state of the fluid dynamic bearing can be evaluated more in detail.